Possibilities of NOx and CHx Determination using Galvanic Cells with Perovskite-Electrodes on YSZ

Perovskite-type mixed oxides with the formula La(1-x)A(x)Me(1-y)B(y)O(3 +/-delta)(x = 0.01 ... 0.2; y = 0.01 ... 0.5; A = Ca, Sr; Me = Cr, Mn, Fe, Co; B = Mg, Ga) were investigated with the aim to use the oxides as electrode materials for galvanic cells with Y2O3-stabilized ZrO2 solid electrolytes (YSZ). The catalytic activity of the oxides for the oxidation, reduction and decomposition of gas components was varied by changing the transition metal and by partial substitution of lanthanum and the metal. The behaviour of different substituted lanthanum chromite/YSZ and manganite/YSZ electrodes in the presence of nitric oxides (NOx) and combustible components (CHx) in gases containing oxygen was investigated. Various electrode combinations were tested in gas-symmetrical cells. For the NO determination cells with a catalytically active Pt electrode and a La0.8Sr0.2MnO3 electrode with a low catalytic activity for the decomposition of NO were used. The results show the possible quantitative measurement at low and constant p(O-2) on the basis of a calibration. For the determination of C(3)H(6)a CHx-sensitive Au and an O-2-sensitive La0.99Sr0.01CrO3 electrode were combined in a potentiometric thick film sensor. In gases containing oxygen with small amounts of C3H6 the sensor provided a utilizable voltage in dependence of the C3H6 concentration.